In about 1951 Dr. Gavriil A. Ilizarov of the Soviet Union developed a technique and supportive equipment for effecting limb lengthening which involves the circumferential severance of the cortex of a bone to be lengthened while minimizing damage to the periosteum and the medullary cavity, and then very gradually separating the severed cortex ends as new bone is generated in the distraction gap. The technique is useful both in the lengthening of initially sound bones in cases of dwarfism and in restoring original bone lengths in which there has been loss of bone through accident of disease.
Since originally developed the technique has been successfully used in about a million cases world-wide although the technique has only quite recently been introduced in the United States.
The supportive equipment, known as the Ilizarov External Fixator, comprises a plurality of rings arranged circumferentially of the limb to be lengthened which are adjustably assembled at appropriate positions longitudinally of the limb to support pins passing through portions of the limb for which relative movement is desired. There are other similar systems on the market as well.
The apparatus can be thought of as a Compression-Distraction Apparatus denoting its capability of both moving bony ends together as needed while at the same time accomplishing distraction at the location of annular severance or corticotomy of the bone cortex in the area where lengthening is desired.
This equipment is distributed in the United States by Richards Medical Company of Memphis, Tenn.; and its nature and use is extensively described and illustrated in a general surgical technique brochure entitled "The Ilizarov External Fixator" which is published and distributed by Richards Medical Company.
The equipment and technique is also extensively discussed in a review article entitled "Current Techniques in Limb Lengthening" by Dror Paley, M.D., F.R.C.S., (C) which appeared in the Journal of Pediatric Orthopedics 8:73-92 (1988).
As there described the Ilizarov technique involves initiation of distraction about seven days following corticotomy at the rate of about 1 mm per day suitably by making 0.25 mm adJustments in the Ilizarov External Fixator four times a day. This distraction rate may be increased or decreased slightly depending on the individual being treated; the important thing being that the distraction rate substantially coincide with the regeneration of cortex, and that it be fast enough to prevent consolidation of regenerated cortex which would prevent further distraction. With the distraction rate properly regulated a bone extension of as much as 6-8 inches can be accomplished by this technique.
The corticotomy according to the Ilizarov technique is accomplished as follows:
(1) Make a 1 cm longitudinal incision just lateral to the tibial crest. Cut down to and through periosteum. Insert a periosteal elevator medially and laterally to elevate the periosteum at the level of the bone cut. Insert a 1 cm osteotome into the rent in the periosteum and turn the osteotome 90 degrees,
(2) Cut into the anterior cortex of the tibia, creating a groove with the osteotome.
(3) The cut should extend to but not through the medullary cavity.
(4) Remove the 1 cm osteotome and carefully insert a periosteal elevator on the lateral side, thus stripping the periosteum and lifting it from the bone. The elevator should reach around the posterolateral cortex. With the elevator lying flat against the bone, the direction of the cut can be appreciated.
(5) Insert a 5 mm osteotome under the protection of the elevator. Cut the cortex down to and through the posterolateral corner. Keep the osteotome in the cortex only. Do not penetrate deeply into the medullary cavity. Do not slide out of the cortex inadvertently. Remove the osteotome by slightly twisting it side to side to loosen it in the bone rather than using a window wiper maneuver which may damage the medullary cavity.
(6) Repeat the same maneuver on the medial side. Cut to and through the posteromedial cortex.
(7) Twist the osteotome, which is located in the posteromedial corner, 90 degrees. This will spread the osteotomy apart like a laminar spreader and begin the osteoclasis of the posterior cortex.
(8) Repeat the same maneuver on the medial side. This should complete the fracture of the posterior cortex. This maneuver may need to be repeated several times on the medial and lateral side until one is convinced that the posterior cortex is broken. Once these maneuvers are completed, rotate the distal ring externally, relative to the proximal ring. This will avoid stretching the peroneal nerve and will complete and ensure the osteoclasis.
In the technique as above described the use of a conventional flat osteotome of 5 mm or other appropriate width in the circumferential cutting of cortex is a delicate operation requiring great care and skill if inadvertent damage to the periosteum or the meduallary cavity is to be prevented. Damage in these areas, and particularly damage to the medullay cavity and the nutrient arteries can complicate and greatly prolong the bone regeneration and the progress of a desired distraction.